Introduce the save_to_well_known_file() method.

oauth2client/appengine.py

@@ -197,6 +197,10 @@ class AppAssertionCredentials(AssertionCredentials):
       raise AccessTokenRefreshError(str(e))
     self.access_token = token
 
+  @property
+  def serialization_data(self):
+    raise NotImplementedError('Cannot serialize credentials for AppEngine.')
+
   def create_scoped_required(self):
     return not self.scope
 

oauth2client/client.py

@@ -985,6 +985,16 @@ class GoogleCredentials(OAuth2Credentials):
     """
     return self
 
+  @property
+  def serialization_data(self):
+    """Get the fields and their values identifying the current credentials."""
+    return {
+        'type': 'authorized_user',
+        'client_id': self.client_id,
+        'client_secret': self.client_secret,
+        'refresh_token': self.refresh_token
+    }
+
   @staticmethod
   def get_application_default():
     """Get the Application Default Credentials for the current environment.
@@ -1004,6 +1014,8 @@ class GoogleCredentials(OAuth2Credentials):
     else:
       application_default_credential_filename = _get_environment_variable_file()
       well_known_file = _get_well_known_file()
+      if not os.path.isfile(well_known_file):
+        well_known_file = None
 
     if application_default_credential_filename:
       try:
@@ -1064,6 +1076,26 @@ class GoogleCredentials(OAuth2Credentials):
           'method should point to a file.')
 
 
+def save_to_well_known_file(credentials, well_known_file=None):
+  """Save the provided GoogleCredentials to the well known file.
+
+  Args:
+    credentials:
+      the credentials to be saved to the well known file;
+      it should be an instance of GoogleCredentials
+    well_known_file:
+      the name of the file where the credentials are to be saved;
+      this parameter is supposed to be used for testing only
+  """
+  if well_known_file is None:
+    well_known_file = _get_well_known_file()
+
+  credentials_data = credentials.serialization_data
+
+  with open(well_known_file, 'w') as f:
+    simplejson.dump(credentials_data, f, sort_keys=True, indent=2)
+
+
 def _get_environment_variable_file():
   application_default_credential_filename = (
       os.environ.get(GOOGLE_APPLICATION_CREDENTIALS,
@@ -1103,8 +1135,7 @@ def _get_well_known_file():
   default_config_path = os.path.join(default_config_path,
                                      WELL_KNOWN_CREDENTIALS_FILE)
 
-  if os.path.isfile(default_config_path):
+  return default_config_path
-    return default_config_path
 
 
 def _get_application_default_credential_from_file(

oauth2client/gce.py

@@ -93,6 +93,11 @@ class AppAssertionCredentials(AssertionCredentials):
             ' with no service account or scopes.')
       raise AccessTokenRefreshError(content)
 
+  @property
+  def serialization_data(self):
+    raise NotImplementedError(
+        'Cannot serialize credentials for GCE service accounts.')
+
   def create_scoped_required(self):
     return not self.scope
 

oauth2client/service_account.py

@@ -92,6 +92,16 @@ class _ServiceAccountCredentials(AssertionCredentials):
   def service_account_email(self):
     return self._service_account_email
 
+  @property
+  def serialization_data(self):
+    return {
+        'type': 'service_account',
+        'client_id': self._service_account_id,
+        'client_email': self._service_account_email,
+        'private_key_id': self._private_key_id,
+        'private_key': self._private_key_pkcs8_text
+    }
+
   def create_scoped_required(self):
     return not self._scopes
 

tests/test_appengine.py

@@ -69,6 +69,7 @@ from oauth2client.client import Credentials
 from oauth2client.client import FlowExchangeError
 from oauth2client.client import OAuth2Credentials
 from oauth2client.client import flow_from_clientsecrets
+from oauth2client.client import save_to_well_known_file
 from webtest import TestApp
 
 
@@ -248,6 +249,10 @@ class TestAppAssertionCredentials(unittest.TestCase):
     self.assertEqual('a_token_123', token.access_token)
     self.assertEqual(None, token.expires_in)
 
+  def test_save_to_well_known_file(self):
+    credentials = AppAssertionCredentials([])
+    self.assertRaises(NotImplementedError, save_to_well_known_file, credentials)
+
 
 class TestFlowModel(db.Model):
   flow = FlowProperty()

tests/test_gce.py

@@ -26,6 +26,7 @@ import unittest
 
 from oauth2client.client import AccessTokenRefreshError
 from oauth2client.client import Credentials
+from oauth2client.client import save_to_well_known_file
 from oauth2client.gce import AppAssertionCredentials
 
 
@@ -131,4 +132,7 @@ class AssertionCredentialsTests(unittest.TestCase):
 
     m.UnsetStubs()
     m.VerifyAll()
-    
+
+  def test_save_to_well_known_file(self):
+    credentials = AppAssertionCredentials([])
+    self.assertRaises(NotImplementedError, save_to_well_known_file, credentials)

tests/test_oauth2client.py

@@ -67,6 +67,7 @@ from oauth2client.client import _update_query_params
 from oauth2client.client import credentials_from_clientsecrets_and_code
 from oauth2client.client import credentials_from_code
 from oauth2client.client import flow_from_clientsecrets
+from oauth2client.client import save_to_well_known_file
 from oauth2client.clientsecrets import _loadfile
 from oauth2client.service_account import _ServiceAccountCredentials
 
@@ -260,11 +261,6 @@ class GoogleCredentialsTests(unittest.TestCase):
     os.environ['APPDATA'] = DATA_DIR
     self.assertEqual(well_known_file, _get_well_known_file())
 
-  def test_get_well_known_file_on_windows_no_file(self):
-    os.name = 'nt'
-    os.environ['APPDATA'] = os.path.join(DATA_DIR, 'nonexistentpath')
-    self.assertEqual(None, _get_well_known_file())
-
   def test_get_application_default_credential_from_file_service_account(self):
     credentials_file = datafile(
         os.path.join('gcloud', 'application_default_credentials.json'))
@@ -272,6 +268,22 @@ class GoogleCredentialsTests(unittest.TestCase):
         credentials_file)
     self.validate_service_account_credentials(credentials)
 
+  def test_save_to_well_known_file_service_account(self):
+    credential_file = datafile(
+        os.path.join('gcloud', 'application_default_credentials.json'))
+    credentials = _get_application_default_credential_from_file(
+        credential_file)
+    temp_credential_file = datafile(
+        os.path.join('gcloud', 'temp_well_known_file_service_account.json'))
+    save_to_well_known_file(credentials, temp_credential_file)
+    with open(temp_credential_file) as f:
+      d = simplejson.load(f)
+    self.assertEqual('service_account', d['type'])
+    self.assertEqual('123', d['client_id'])
+    self.assertEqual('dummy@google.com', d['client_email'])
+    self.assertEqual('ABCDEF', d['private_key_id'])
+    os.remove(temp_credential_file)
+
   def test_get_application_default_credential_from_file_authorized_user(self):
     credentials_file = datafile(
         os.path.join('gcloud',
@@ -280,6 +292,23 @@ class GoogleCredentialsTests(unittest.TestCase):
         credentials_file)
     self.validate_google_credentials(credentials)
 
+  def test_save_to_well_known_file_authorized_user(self):
+    credentials_file = datafile(
+        os.path.join('gcloud',
+                     'application_default_credentials_authorized_user.json'))
+    credentials = _get_application_default_credential_from_file(
+        credentials_file)
+    temp_credential_file = datafile(
+        os.path.join('gcloud', 'temp_well_known_file_authorized_user.json'))
+    save_to_well_known_file(credentials, temp_credential_file)
+    with open(temp_credential_file) as f:
+      d = simplejson.load(f)
+    self.assertEqual('authorized_user', d['type'])
+    self.assertEqual('123', d['client_id'])
+    self.assertEqual('secret', d['client_secret'])
+    self.assertEqual('alabalaportocala', d['refresh_token'])
+    os.remove(temp_credential_file)
+
   def test_get_application_default_credential_from_malformed_file_1(self):
     credentials_file = datafile(
         os.path.join('gcloud',